Jacket crown, model, and method of applying



Feb. 28, 1933. L. L. FOSTON 1,899,713

JACKET CROWN, MODEL, AND METHOD OF APPLYING Filed March 25, 1928 FIG-3 9 we FIG-6 FlG.-9 FlC.-IO

\NITNE9SES 5 IN VENTOR Patented Feb. 28, 1933 LEON LEROY iPOS'lON, or vI-N roN, IOWA JACKET onown, MODEL, AND METHOD or APPLYING Application filed March 23,

My invention relates to the art of dentistry where an injured tooth is to be restored to good appearance and function by means of a hollow [porcelain tooth form, commonly known as a porcelain jacket crown and the object of my invention is:

To provide a procedure with appliances whereby much time now consumed can be saved in thus restoring teeth,

" To-provide means whereby .much of the exacting skill .now required to make such a res- .toration, may be dispensed with and at the samef'time more satisfactory results bemore I surely attained.

I attain these objects in the following mannerand by the structure illustrated inthe accompanyingdrawing in which 1 is anatural tooth badly decayed and calling for a porcelain jacket crown.

Fig. 2 is the same tooth trimmed down ready to receive such a crown.

Fig. Bis a porcelain jacket crown.

Fig. 4is the crown in place on tooth but not trimmed .to match the neck surface-circumference.

' "Fig. 5 shows the same after it has been trimmed to match.

Fig. 6 is a section of a porcelain crown, frontview.

Fig. 7 is a sectional side view of same.

f'Fig. Sis a'socket former, with a projection Bofthe sizeand shape of a prepared natural tooth, .the ridge WV, the gateway H and the removable handle K, all showing. p

9 shows agate forthe gateway H in socket-former of Fig. 8.

Fig. 10 is an end View.of'socketsformer.

.Fig. 11 is a molding ring showing slots P. P. P. g p

F ig. 12is an end view of same, ring showing the sepaiating strips R in slots and side view of'stripR.

LF liiisa sectional view of a molding ring Tointowhich is placed the socket-former with tooth-model B. "Gate I is in place and a crown M "is on model B. Separating strip R in "slot 'andthe balance of hole in ring filled. with investment N. 'Fig. l4-is'a section of same ring'T with the investment N re-assembled in place.

1928. Serial No. 36mm.

Fig. 15 shows the same as 14;, but withjlow fusing metal S in mold where' porcelain crown was. p

' Fig. 16 is a sectional view of same ringjT and investment N with fusible metalS into .55 which has been pressed socketfor1ner B causing the fused metal to flow out thru gateway as S8. i i

Like'letters'refer to the san'ie'parts through.- V out the several views. i

Porcelain jacket crowns are first made upin stock oi various sizes forinsand shades'to meet all requirements. a

For a given case, a crown is selectedto match the natural teeth. This-is then pl ed e th s ck ermer nmdeiorit, (can Z of socket v ng- ,s ke i rmel'to onfo m to itself) all of which then placed inthe largeend of molding 'ring. r v

Separating strips areplaced in slots and the remainder of the ring is filled within? vestment made oi? some material like plaster of Paris that will flow andthen set to form a mold, all as shown in Fig.1'13. N

hen the investment is set, all is lpushed out of the large end ofzring and the separating strips are withdrawn. The investment isthen split away from crown andre-assem bled in molding .ring as shown i -n llig. :14, Tbeing the ring, N the investment. 8o Into this is poured some low-fusing metal as S .inFig. l5 and into this fused metal is pressed after'it'h'as been heated,thelsoc'ketformer B causing the excessmetal toflow away-thru the gateway ;H which has been made by removing gate I. This excess metal is shown as S8. Thus we have a metal model of the porcelain crown to guide us in cutting down the tooth end to fit the porcelain crown. But to give additional he1p,we have socketformers of larger sized B,parts,to nakeseniiduplicates of the crown; that inbeing larger will go over-the tooth end before the tooth end is so near ofa' size. to the porcelain crown. These can be of one or moreis zes larger than the exact duplicateand be used at the beginning of thetooth trimming using the largest one, first, then the next smaller.

'Solmving these .c1: wn ;ot metal, w now proceed to prepare thetoothen'd. "First cutting away only part of as much as we can see Wlll be necessary, or ust enough to rece1vc mark on the tooth where the tooth needs to be trimmed more. Then these high points are trimmed away, the metal crown is again tried on and in such manner the tooth is worked down until a loose fit is obtained of this largest metal crown. Then the next smaller metal crown is used the same way to still further reduce the natural tooth.

lVhen this becomes a loose iit, the metal crown that is an exact duplicate of the porcelain crown is used in the same manner as the others but the trimming is done with more care and we stop as soon as the metal crown will go to place. In this way the trimming of the tooth can'be done with great accin'acy and since the porcelain crown is not tried on until the trimming, is all done, there is little danger of breakage of this fragile porcelain.

But to give added protection to the porcelain crown, I propose to have them made with an additional thickness around the neck end of the tooth. This extra thickness not only gives strength but is also often needed to provide a surplus of porcelain at this point so it may be dressed away after the fitting is completed, tocome flush with the circumference-surface oi the natural tooth, which is of such a variety of irregular curves that unless there was a surplus all around the porcelain crown, there might be insufficient porcelain to make a good flush finish. This extra thickness is shown as G C Figs. 3 and 4. i In cementing a porcelain jacket crown to place on a prepared tooth, there is danger of either not getting the crown to go all the way to place because the cement doesnt have a way of escape and packs in the bottom of the socket; or there is danger of breaking the porcelain crown because of the pressure necessary to press the surplus cement out of the socket when a close fit is procured. To overcome these two difliculties, I propose to have the crowns made with one or more small grooves running from near the.

bottom of the socket to the outer edge as shown in Figs. 6 and 7.

These grooves need not be deep to provide gateway for the surplus cement to escape, thus allowing the crown to go to place with very little pressure.

I am aware that porcelain crowns have been in use -for many years whereby injured teeth have been restored to usefulness, but inthe past, none have had the groove or gateway to allow the escape of the sulplus cement, neitherhave they been made with a surplus of porcelain at the neck end as I have described to give strength andallow fitting. Also, in the past such porcelain jacket crowns were made to fit a tooth that had first been trimmed or prepared, while, I reverse the procedure by trimming the tooth to fit a crown that is already made up.

In the past the tooth was prepared in suitable shape for such a crown. A thin plati' num matrix was then made to fit this pre pared tooth. Over this matrix, a crown was built up and carved to look something like the tooth should. This required great skill and much time and because the shape changed in the baking, it'was not an easy matter to get the shape and size right. Then too, the color or shade was very diflicult to get right as it too changed in the baking.

Because of the great skill required and the time consumed, there are only a very few dentists using the porcelain jacket crown, first, because the fee for making one as now done, must necessarily be too high for the general public to feel they can atlonl it, second, because the skill required is more ban the ave age dentist has developed.

Since with my PI'OCBCllll'B and improved crowns all made, most of the exacting skill is dispensed with as all that is necessary is a good eye to know a good match when it is placed side by side and the mechanical skill suiiicient to trim the tooth to fit. All this the dentist, it he is allowed to practice dentistry, should do with ease.

Thus placing this most desirable of all restorations in the hands of all dentists wnere the general public can be served at prices within their reach, prices being re duced by the reduction in the time necessary to make the restoration and because it requires no special training and but little extra equipment.

Having thus described my invention, what I claim and what I desire to secure by Letters Patent is:

1. The process of reducing a natural tooth enough and in such manner, that itwill enter and approximately fit the socket 0t a'porcelain crown, usmg "for measuring and marking the tooth, while it is being reduced, duplicates as to size and form of theexterior of the crown, while the sockets graduate from a duplicate to one or more sizes larger which comprises reducing the tooth tofit large'oven size sockets, then reducing the tooth to successively fit theintermediate oversize sock-- ets, and then reducing the tooth to fit a duplicate socket of the porcelain crown.

2. The method of makingmetal duplicates and semi-duplicates of porcelain jacket crowns, which comprises embedding the crown in investment to form the moldtor the outer surface of the crown and removing the crown. and inserting a metal socket-former, having the desired relative size to complete the mold, whereby a metal duplicate or semiduplicate of the porcelain crown may be made.

3. A metal model of a natural tooth after it has been prepared to receive a porcelain crown, said model extending from a base,

said base having a groove or gatewa run ning from near the junction of the mod el and the base, to the bottom of the base, said gateway being provided with a gate to be used when desired.

4. A metal model of a natural tooth after it has been prepared to receive a porcelain jacket crown, extending from a base, said base having a removable handle extending from its bottom and said base having a gateway running from near the junction of the model and the base to the bottom of the base and said gateway being provided with agate.

5. A metal model of a natural tooth after it has been prepared to receive a porcelain jacket crown, said model extending from a 29 base said base having a gateway running from near the junction of the model and the base to the bottom of the base and said base having a ridge extending across the edge thereof.

6. A metal model of a natural tooth after it has been prepared to receive a porcelain jacket crown, said model extending from a base, said base having a ridge extending across its edge and a removable handle extending 39 from its bottom and a gateway or groove running from near the junction of the model and the base to the bottom of the base, said gateway being provided with a gate to be A used when desired.

7. The method of reducing and reshaping a natural tooth to a form generally accepted as the best shape to receive a porcelain jacket crown, by means of markers of suitable metal, having sockets formed in duplicate and semiduplicates of the porcelain crown to be used, which comprises first, roughly reducing the natural tooth to size and form that will allow the metal semi-duplicate with the largest socket to be forced thereon, whereby it will mark the tight places; the tooth being then reduced at these points to allow the semiduplicate with the next smaller socket to be forced thereon to mark where the tooth should be further reduced, and in like manner the tooth is further reduced, using markers with successively smaller sockets until the one that is a duplicate of the crown can be used to make the final marks for the finished reduction to make a good fit of the porcelain crown.

In testimony whereof, I have signed my name to this specification.

LEON LEROY POSTON. 

